The Great Barrier Reef Marine Park Authority said the four undetonated bombs posed little risk to wildlife or reef. Photograph: AIMS/AFP/Getty Images

A joint US-Australian search mission has located the four undetonated bombs that were dropped on to the Great Barrier Reef marine park in a botched military drill last month.

The Department of Defence said the royal Australian navy’s mine-hunter HMAS Gascoyne had located all of the ordnance on Friday.

The Australian navy will now help the US navy’s USS Germantown retrieve the bombs.

A Defence spokeswoman couldn’t confirm to Guardian Australia exactly when the retrieval would take place, but that it would depend on weather and environmental considerations.

The bombs were dropped into the sea by US aircraft that had run dangerously low on fuel. The aircraft were trying to bomb a small island in the Great Barrier Reef marine park in a drill conducted ahead of Talisman Saber, a biannual US-Australian training exercise that includes various war games.